Independent Thread Scheduling
Warp Execution and Divergence described divergence as a cost model: a warp pays for every path its lanes take. Before Volta, divergence was also a scheduling model with sharp edges — the hardware tracked one program counter per warp using an explicit reconvergence stack, and code that assumed lockstep execution within a warp could rely on undocumented but consistent scheduling behavior. Volta replaced that mechanism, and the change is why so many older warp-synchronous idioms are now silently broken rather than merely non-portable.